The object of the present invention is a process for removing halogenated impurities from olefins.
French Pat. No. 2 443 877 discloses an improved catalytic composition and its use as an oligomerization catalyst for monoolefins, for example those having from 2 to 4 carbon atoms and particularly as a dimerization and/or trimerization catalyst therefor. This catalytic composition consists of the product obtained by contacting, in any order, a bivalent nickel compound with a hydrocarbyl aluminum halide and an organic Bronsted acid, preferably a halogenocarboxylic acid, for example trichloracetic acid or trifluoracetic acid. However an additional problem has appeared: all or part of the halogen is found in the resultant olefinic oligomerizate, which is unacceptable for a number of uses of this oligomerizate. The difficulty of removing the traces of halogen was then encountered. In view of the acidic nature of the halogenated compounds introduced into the catalyst, it could be expected that washing the oligomerizate with water or with a base in aqueous medium would remove these traces of halogen. The failure of this method shows that the problem has no obvious solution and that the halogen is probably engaged in the form of a compound soluble in hydrocarbons and which cannot be extracted easily.